In life, there will be death. However, many people do not understand the criteria and process of judging death. How can death be considered? What changes will happen to your body when you are on the verge of death? How should we face death? Does humans have a way to defeat death? Next, let us think carefully about how to view death scientifically.
There are four parts in this article. The following mind map summarizes the structure directory of this article.
Part 2: What changes will happen to the body that is heading towards death?
The heart stops beating, the consciousness disappears, and the body gradually becomes stiff - after a person dies, the body will undergo various changes. People maintain life activities through the work of various organs and tissues such as the heart, lungs, brain, and muscles. So, what changes will happen to these organs and tissues when they go from "life" to "death"? Part 2 will introduce the unique phenomena and changes that occur in the body as it moves toward death.
1. Organ function stop
The heart is closely related to the organs throughout the body. The "negative circulation" causes the heart to stop beating
The heart stop beating will directly lead to death. So, what happens if other organs stop working?
If the lung function decreases or even stops breathing for some reason, the blood will be deficient in oxygen, which will eventually lead to the myocardium being unable to continue to move.
In addition, as introduced in Part 1, if the brain stem function is lost, the person cannot maintain breathing and heartbeat, and the heart will stop working.
0 pulmonary function decline
0 intestinal function decline
brain stem loses function
00 liver function decline
00 kidney function decline
2. Cardiac arrest
Heartbeat sometimes stops
According to statistics, there are as many as 200,000 people who die from heart disease every year, ranking second in the cause of death. Among them, more than 70,000 people die suddenly of due to heart disease every year. Even if there are no conscious symptoms in daily life, the heart will sometimes stop beating suddenly. The representative reason is " myocardial infarction ".
Artery blockage causes myocardial infarction
Myocardial infarction (referred to as "myocardial infarction") is a heart disease caused by the blockage of coronary artery surrounding the outer side of the heart. The coronary artery is responsible for providing the oxygen and nutrients needed by the myocardium. Therefore, coronary artery blockage will hinder the downward delivery of oxygen and nutrients. After a few dozen minutes, the myocardium will die, which will eventually cause the heart to stop beating. When a myocardial infarction occurs, there will be severe pain in the chest . If not treated in time, it may be life-threatening. Patients with atherosclerosis will have raised plaques (atheromas) on the walls of blood vessels, and blood clots will form after rupture, which is one of the causes of coronary artery blockage.
Ventricular fibrillation will cause sudden loss of consciousness
In addition to myocardial infarction, another heart disease - ventricular fibrillation (referred to as "ventricular fibrillation") can also cause sudden death. Ventricular fibrillation refers to the state where the heart is twitching rapidly, unable to beat normally, and unable to deliver blood to the whole body. After a few seconds of ventricular fibrillation, the person will lose consciousness and stop breathing.
If you use automatic external defibrillator (AED) within 10 minutes, the heart may resume normal beating and save lives.
3. The last brain signal
The "last brain signal" generated when dying
After the heart stopped beating, the brain activity was still active, but the research team at the University of Michigan in the United States had such a shocking conclusion in the paper published in 2013. The study claimed that the experimental results conducted by 9 mice showed that after the heartbeat stopped beating, there was a significant brain wave with a frequency of 30 to 100 Hz (i.e., an electroencephalopathy with 30 to 100 vibrations per second) in the mouse brain, and lasted for 30 seconds. This brain wave, called "gamma wave", is a brain wave related to perception and consciousness, which can usually be observed when a person is staring at something or focusing on something.
4. Brain cells die
After the heart stops beating, brain cells starts to die
After the heart stops beating and blood flow is interrupted, the nerve cells (neurons) in the brain will be affected first. Neurons absorb and consume a lot of oxygen and nutrients from the blood (such as glucose ). Although the brain only accounts for about 2% of the body weight, the brain consumes 20% of the oxygen and energy.
calcium ions flow in large quantities, and the death of neurons
Neurons will use the absorbed oxygen and glucose as "raw materials" to generate energy source "adenosine triphosphate" (ATP) in mitochondrial .
neurons use ATP to maintain the balance between inside and outside the cells and maintain normal activity.
However, when the blood flow stops, the supply of oxygen and glucose is interrupted, and the neurons cannot continue to generate ATP. In this way, neurons cannot maintain balance, and a large amount of calcium ions will pour in from the surroundings, which will eventually lead to the death of the neurons.
The blood flowing to the brain will be interrupted for 10 seconds, and brain function will decline and you will lose consciousness. After stopping supplying oxygen and glucose to the neurons, the neurons die within a few minutes.
Neurons
Once the supply of oxygen and nutrients is interrupted, the neurons will die
Neuron discharge diagram
4. After death, stiffness
After death, the muscles in the whole body will become stiff
Muscle composition
After death, various changes will occur in the body.
Among them, the most well-known one is " after death, stiff ".
After death, stiffness refers to the state in which the muscles in the body become hard after death, and others cannot move even if they want to move the joints of the deceased.
After death, stiffness gradually forms from head to toe. First, 2 to 3 hours after death, the jaw and neck begin to stiffen, and then gradually expand in the order of shoulders, arms, legs, fingers, and toes. About 6 to 8 hours after death, the joints of the whole body become hard, and the stiffness reaches its peak 12 to 15 hours after death, and the body is the most stiff.
The stiffness will last about 24 to 36 hours after death, and then gradually disappear in the order of occurrence. The time and degree of stiffness after death will vary depending on the temperature and the amount of muscles of the deceased.
Why do people become stiff after death?
After people die, blood stops flowing, the supply of oxygen and nutrients is interrupted, and ATP will be consumed. Moreover, sarcoplasmic reticulum is damaged and the calcium ions in myofibrils cannot be recovered. As a result, the binding between actin filaments and myosin filaments cannot be lifted and will remain in a contraction state, resulting in muscle stiffness.
Next we will continue to share the third part, thank you for reading.
Quote from: World of Science August 2021 issue
